import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Queue;

public class BinaryTree {

    static class TreeNode {
        public char val;
        public TreeNode left;//左孩子的引用
        public TreeNode right;//右孩子的引用

        public TreeNode(char val) {
            this.val = val;
        }

        @Override
        public String toString() {
            return "找到了：" +
                    "TreeNode{" +
                    "val=" + val +
                    '}';
        }
    }


    /**
     * 创建一棵二叉树 返回这棵树的根节点
     *
     * @return
     */
    public TreeNode createTree() {
        TreeNode a = new TreeNode('A');
        TreeNode b = new TreeNode('B');
        TreeNode c = new TreeNode('C');
        TreeNode d = new TreeNode('D');
        TreeNode e = new TreeNode('E');
        TreeNode f = new TreeNode('F');
        TreeNode g = new TreeNode('G');
        TreeNode h = new TreeNode('H');
        a.left = b;
        a.right = c;
        b.left = d;
        b.right = e;
        c.right = f;
        d.left = h;
        e.right = g;
        return a;
    }

    // 前序遍历
    public void preOrder(TreeNode root) {
        if(root == null){
            return;
        }
        System.out.println(root.val);
        preOrder(root.left);
        preOrder(root.right);
    }

    // 中序遍历
    void inOrder(TreeNode root) {
        if(root == null){
            return;
        }
        inOrder(root.left);
        System.out.println(root.val);
        inOrder(root.right);
    }

    // 后序遍历
    void postOrder(TreeNode root) {
        if(root == null){
            return;
        }
        postOrder(root.left);
        postOrder(root.right);
        System.out.println(root.val);
    }

    public static int nodeSize;

    /**
     * 获取树中节点的个数：遍历思路
     */
    void size(TreeNode root) {
        if(root == null)
            return;

        nodeSize++;
        size(root.left);
        size(root.right);
    }

    /**
     * 获取节点的个数：子问题的思路
     *
     * @param root
     * @return
     */
    int size2(TreeNode root) {
        if (root == null)
            return 0;

        int leftNode = size2(root.left);
        int rightNode = size2(root.right);

        return leftNode + rightNode + 1;
    }


    /*
     获取叶子节点的个数：遍历思路
     */
    public static int leafSize = 0;

    void getLeafNodeCount1(TreeNode root) {
        if(root == null)
            return;

        if(root.left == null && root.right == null)
            leafSize++;

        getLeafNodeCount1(root.left);
        getLeafNodeCount1(root.right);
    }

    /*
     获取叶子节点的个数：子问题
     */
    int getLeafNodeCount2(TreeNode root) {
        if(root == null)
            return 0;
        if(root.left == null && root.right == null)
            return 1;
        int leftLeaf = getLeafNodeCount2(root.left);
        int rightLeaf = getLeafNodeCount2(root.right);
        return leftLeaf + rightLeaf;
    }

    /*
    获取第K层节点的个数
     */
    int getKLevelNodeCount(TreeNode root, int k) {
        if(root == null)
            return 0;
        if(k == 1)
            return 1;
        int leftK = getKLevelNodeCount(root.left, k - 1);
        int rightK = getKLevelNodeCount(root.right, k - 1);
        return leftK + rightK;
    }

    /*
     获取二叉树的高度
     时间复杂度：O(N)
     */
    int getHeight(TreeNode root) {
        if(root == null)
            return 0;
        int leftHeight = getHeight(root.left);
        int rightHeight = getHeight(root.right);

        return Math.max(leftHeight, rightHeight) + 1;
    }


    // 检测值为value的元素是否存在
    TreeNode find(TreeNode root, char val) {
        if(root == null){
            return null;
        }

        if(root.val == val){
            return root;
        }

        TreeNode left = find(root.left, val);
        if(left != null){
            return left;
        }

        TreeNode right = find(root.right, val);
        if(right != null){
            return right;
        }
        return null;
    }

    //层序遍历
    void levelOrder(TreeNode root) {
        if(root == null)
            return;
        Queue<TreeNode> queue = new ArrayDeque<>();
        queue.offer(root);
        while(!queue.isEmpty()){
            TreeNode tmp = queue.poll();
            System.out.println(tmp.val);
            if(tmp.left != null)
                queue.offer(tmp.left);
            if(tmp.right != null)
                queue.offer(tmp.right);
        }
    }


    // 判断一棵树是不是完全二叉树
    boolean isCompleteTree(TreeNode root) {
        if(root == null)
            return true;
        ArrayDeque<TreeNode> queue = new ArrayDeque<>();
        queue.offer(root);
        int flag = 0;
        while(!queue.isEmpty()){
            int size = queue.size();
            for(int i = 0; i < size; i++){
                TreeNode tmp = queue.poll();
                if(flag == 1){
                    if(tmp.left == tmp.right && tmp.left == null){

                    }else{
                        return false;
                    }
                }
                if(tmp.left == null){
                    if(tmp.right != null)
                        return false;
                    else
                        flag = 1;
                }else{
                    queue.offer(tmp.left);
                    if(tmp.right == null)
                        flag = 1;
                    else
                        queue.offer(tmp.right);
                }
            }
        }
        if(queue.isEmpty())
            return true;
        else
            return false;
    }

    public static void main(String[] args) {
        BinaryTree tree = new BinaryTree();
        TreeNode root = tree.createTree();
        System.out.println(tree.getKLevelNodeCount(root, 2));
        System.out.println(tree.getHeight(root));
        //System.out.println(tree.find(root, 'G'));
        tree.levelOrder(root);
    }
}